Process for Purifying Sulphuric Acids

ABSTRACT

The present invention relates to a process for purifying sulphuric acids, in particular metal-containing sulphuric acids, characterized in that monodisperse ion exchangers having chelating functional groups are used.

The present invention relates to a process for purifying sulphuricacids, in particular metal-containing sulphuric acids, usingmonodisperse ion exchangers containing chelating functional groups.

The removal of impurities from sulphuric acids, particularly preferablyfrom copper electrolytes containing sulphuric acids, has recently beenbecoming increasingly important. This process is employed, for example,before cathodic deposition of copper in electrolytic processes carriedout in copper winning or refining processes. The task here is theremoval of metals which can occur in the oxidation state +III.

U.S. Pat. No. 4,559,216 describes a process for removing antimony,bismuth or iron from copper electrolytes containing sulphuric acid usingheterodisperse ion exchangers having specific chelatingaminomethylenephosphonic acid groups. For example, Unicellex® UR 3300 ismentioned there. U.S. Pat. No. 5,366,715 describes a process forremoving antimony, bismuth or iron from copper electrolytes containingsulphuric acid by means of heterodisperse ion exchangers functionalizedwith aminomethylenephosphonic acid, preferably Duolite™ C-467, with areduction of iron(III) to iron(II) firstly being carried out. In U.S.Pat. No. 6,153,081, the abovementioned reduction of iron(I) to iron(II)is carried out using copper and sodium chloride in sulphuric acid andafter the ion exchanger has been laden with the impurities it issubjected to a specific elution in order to selectively isolate bismuthand then antimony. Use is once again made of heterodisperse chelatingexchangers, preferably Epolas® MX-2 from Miyoshi Oil Co., Duolite™ C-467or Unicellex® UR 3300.

All the processes suffer from poor kinetics, selectivity and stabilityof the ion exchangers used. It is therefore an object of the presentinvention to provide a new process for purifying sulphuric acids,preferably for purifying metal-containing sulphuric acids, which makesit possible to remove impurities such as iron, antimony or bismuthselectively in copper winning or refining processes without the ionexchanger used becoming exhausted too quickly. It has now surprisinglybeen found that the abovementioned properties can be improved when ionexchangers having a uniform particle size (hereinafter referred to as“monodisperse”) are used.

The particle size of the ion exchangers used according to the inventionis from 5 to 500 μm, preferably from 10 to 400 μm, particularlypreferably from 20 to 300 μm. For the purposes of the present patentapplication, monodisperse ion exchangers are ion exchangers which have asmall width of the particle size distribution. Customary methods such assieve analysis or image analysis are suitable for determining the meanparticle size and the particle size distribution. The ratio of the 90%value Ø (90) and the 10% value Ø (10) of the volume distribution isemployed as measure for the width of the particle size distribution ofthe ion exchangers used according to the invention. The 90% value Ø (90)is the diameter at which 90% of the particles have a smaller diameter.Correspondingly, 10% of the particles have a diameter smaller than thediameter of the 10% value Ø (10). Monodisperse particle sizedistributions for the purposes of the invention are distributions suchthat Ø (90)/Ø (10)≦1.50, preferably Ø (90)/Ø (10)≦1.25, veryparticularly preferably Ø (90)/Ø (10)≦1.20.

Monodisperse ion exchangers can be obtained by functionalization ofmonodisperse bead polymers. One possible way of preparing monodispersebead polymers is to generate monodisperse monomer droplets by means ofspecific spraying techniques and curing these by polymerization. Theformation of a uniform droplet size can be effected by vibrationalexcitation, as described, for example, in EP-A 0 051 210. If the degreeof monodispersity of the monomer droplets is to be retained in thepolymerization, agglomeration and coalescence and also formation of newdroplets has to be reliably prevented. A particularly effective methodof preventing agglomeration and coalescence and formation of newdroplets is microencapsulation according to EP-A 0 046 535.

Various ways of preparing monodisperse ion exchangers having chelatingfunctional groups (hereinafter referred to as “monodisperse chelatingresins”) are known. U.S. Pat. No. 4,444,961 describes a process forpreparing monodisperse, macroporous chelating resins. Here,haloalkylated polymers are aminated and the aminated polymer is reactedwith chloroacetic acid to form chelating resins of the iminodiaceticacid type. An alternative route is functionalization via a phthalimidestage, which is described in EP-A 1 078 690 for a monodisperse chelatingresin. Both the contents of U.S. Pat. No. 4,444,961 and the contents ofEP-A 1 078 690 are incorporated by reference into the presentdescription.

The present invention achieves this object by providing a process forpurifying sulphuric acids, preferably metal-containing solutionscontaining sulphuric acid, particularly preferably copper electrolytescontaining sulphuric acid, characterized in that metals, particularlypreferably metals which can be present as anions or cations,particularly preferably metals which can be present in the oxidationstate +III, are treated with monodisperse ion exchangers havingchelating functional groups, preferably of the aminomethylenephosphonicacid type or whose functionalization has been effected via thephthalimide stage.

According to the invention, contaminated sulphuric acids as are obtainedin industrial production processes, preferably metal-containingsulphuric acids, particularly preferably copper electrolytes whichcontain sulphuric acid and, in addition to copper, contain furthermetals such as iron, antimony or bismuth, can be worked up in this wayand returned to the industrial production processes.

In the case of copper winning, there are various ways in which ametal-containing sulphuric acid can be produced. In the first method,copper-containing milled ore is extracted with sulphuric acid and the pHis subsequently increased by addition of alkalis. Copper and othermetals are extracted from this ore/sulphuric acid slurry by means of oneor more extractants. The extractant phase is separated off and themetals are reextracted into the sulphuric acid phase by addition ofsulphuric acid. This sulphuric acid is then used as metal-containingsulphuric acid in the process of the invention.

In the production of sulphuric acid by this method for the purificationprocess of the invention, it is also possible to use extractants ormixtures of sulphuric acid with a plurality of extractants. Suitableextractants are substances which form one or more phases in the presenceof sulphuric acid and preferentially dissolve a metal, in the case ofcopper winning copper, in ionic or complexed form. Preferred extractantsare aliphatic or aromatic or mixed aliphatic and aromatic organiccompounds having functional groups. Preferred functional groups are, forexample, phosphate (e.g. in trialkyl phosphate), aldoxime, ketoxime,alcohol, ketone, β-diketone, ester and sulphonamide.

In a further alternative embodiment, elemental copper contaminated withmetals which can occur in the oxidation state +III is brought intosolution in the presence of sulphuric acid by anodic oxidation in anelectric field. Such sulphuric acid can also be used as appropriatemetal-containing sulphuric acid in the process of the invention.

The concentration of these sulphuric acids can vary within a wide range.The preferred sulphuric acid concentration for the process of theinvention is 50-500 g/l, particularly preferably 75-400 g/l, veryparticularly preferably 125-275 g/l.

The amounts of metals in the sulphuric acid to be used according to theinvention, in particular the amount of copper and the amounts of othermetals, can fluctuate within a wide range and are dependent on thequality of the ore and the extraction process. In the case of copperwinning, the preferred concentration of copper in the sulphuric acid is5-100 g/l, particularly preferably 20-50 g/l, very particularlypreferably 25-35 g/l.

In the process of the invention, preference is given to removing metalswhich can occur in the oxidation state +III from the sulphuric acids.Preferred metals are one or more metals of the group consisting ofantimony, bismuth, arsenic, cobalt, nickel, molybdenum and iron.Particularly preferred metals are one or more metals from the groupconsisting of antimony, bismuth and molybdenum, very particularlypreferably antimony or bismuth. The preferred antimony concentration is0-5 g/l, particularly preferably 0-2 g/l, very particularly preferably0.1-1 g/l. The preferred bismuth concentration is 0-5 g/l, particularlypreferably 0-2 g/l, very particularly preferably 0.1-1 g/l.

The process of the invention can be carried out continuously orbatchwise. Preference is given to continuous processes. Here, the resinis employed in a column provided with perforated plates. Here, the speedat which the sulphuric acid to be purified travels through the columnshould be chosen so that a high volume flow passes through the columnbut elevated concentrations of the metals to be removed do not remain inthe stream leaving the column. The preferred flow rate through thecolumn is 5-30 times the ion exchanger bed volume per hour (this unit ishereinafter referred to as bed volume per hour (BV/h)), particularlypreferably 10-20 BV/h.

As a result of the use of the ion-exchange resin according to theinvention, the metals to be removed accumulate in the ion-exchangeresin. These can be eluted by setting conditions under which thechemical affinity of the metals to the ion-exchange resin is reduced. Aneffective method of eluting ion exchangers is treatment with mineralacids or organic acids, preferably in a concentration of 0.1-10 eq/1.Elution is usually carried out using 1-10 bed volumes (BV), preferably2-5 BV. Preferred mineral acids are hydrochloric acid or sulphuric acid,while preferred organic acids are acetic acid, formic acid or tartaricacid. Organic salts (e.g. tartrates) or inorganic salts (e.g. sodiumchloride) can also be present during elution.

The sulphuric acid purified by means of the monodisperse chelatingexchanger can finally be used directly in electrolytic processes for theproduction of elemental copper by reduction of the cathode.

Functional groups in the monodisperse chelating exchangers usedaccording to the invention can be all chelate-forming functional groups.Preference is given to functional groups of the type

—(CH₂)_(n)—NR₁R₂

where—R₁ is hydrogen or a CH₂—COOH or CH₂—P(O)(OH)₂ radical andR₂ is a CH₂—COOH or CH₂—P(O)(OH)₂ radical andn is an integer from 1 to 4.

Particular preference is given to functional groups of the type—(CH₂)_(n)—NR₁R₂

in whichR₁ is hydrogen or the radical CH₂P(O)(OH)₂,

R₂ is CH₂P(O)(OH)₂ and

n is 1, 2, 3 or 4.

Preference is likewise given to all anionic forms or salts of metals inthe oxidation states +I and +II which are formed by abstraction orreplacement of the acidic hydrogen of the functional group.

As polymer base of the monodisperse chelating exchangers to be usedaccording to the invention, various basic structures are known. It iscustomary to employ ion exchangers based on crosslinked vinylaromaticpolymers and ion exchangers based on condensation products ofhydroxyaromatics and formaldehyde. However, ion exchangers based onaliphatic polyamines, polyesters or natural products, e.g. cellulose orwood, are also known. According to the invention, preference is given tomonodisperse chelating exchangers based on crosslinked vinylaromaticpolymers.

The monodisperse, crosslinked, vinylaromatic base polymer can beprepared by methods known from the literature. For example, such methodsare described in U.S. Pat. No. 4,444,961, EP-A 0 046 535, U.S. Pat. No.4,419,245, WO 93/12167.

A possible copolymer for the purposes of the present invention is, forexample, a copolymer composed of a monovinylaromatic compound and apolyvinylaromatic compound.

As monovinylaromatic compounds, preference is given, for the purposes ofthe present invention, to monoethylenically unsaturated compounds suchas styrene, vinyltoluene, ethylstyrene, α-methylstyrene, chlorostyrene,chloromethylstyrene, alkyl acrylates and alkyl methacrylates.

Particular preference is given to using styrene or mixtures of styrenewith the above-mentioned monomers.

Polyvinylaromatic compounds which are preferred for the purposes of thepresent invention are multifunctional ethylenically unsaturatedcompounds such as divinylbenzene, divinyltoluene, trivinylbenzene,divinylnaphthalene, trivinylnaphthalene, 1,7-octadiene, 1,5-hexadiene,ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate orallyl methacrylate.

The polyvinylaromatic compounds are generally used in amounts of 1-20%by weight, preferably 2-12% by weight, particularly preferably 4-10% byweight, based on the monomer or its mixture with further monomers. Thetype of polyvinylaromatic compounds (crosslinkers) is selected with aview to the later use of the spherical polymers. Divinylbenzene issuitable in many cases. Commercial divinylbenzene grades which containethylvinylbenzene in addition to the isomers of divinylbenzene aresatisfactory for most applications.

In a preferred variant for preparing monodisperse chelating exchangersto be used according to the invention, microencapsulated monomerdroplets are used as bead polymers. The microencapsulation of themonomer droplets can be by means of the materials known for use ascomplex coacervates, in particular polyesters, natural and syntheticpolyamides, polyurethanes, polyureas.

A particularly useful natural polyamide is, for example, gelatin. Thisis employed, in particular, as coacervate and complex coacervate. Forthe purposes of the invention, gelatin-containing complex coacervatesare, in particular, combinations of gelatin with syntheticpolyelectrolytes. Suitable synthetic polyelectrolytes are copolymerscontaining built-in units of, for example, maleic acid, acrylic acid,methacrylic acid, acrylamide and methacrylamide. Particular preferenceis given to using acrylic acid and acrylamide. Gelatin-containingcapsules can be cured by means of customary curing agents such asformaldehyde or glutaraldehyde. The encapsulation of monomer droplets bymeans of gelatin, gelatin-containing coacervates and gelatin-containingcomplex coacervates is described in detail in EP-A 0 046 535. Methods ofencapsulation using synthetic polymers are known. One well-suited methodis, for example, phase interface condensation in which a reactivecomponent (for example an isocyanate or an acid chloride) dissolved inthe monomer droplet is reacted with a second reactive component (forexample an amine) dissolved in the aqueous phase.

The optionally microencapsulated monomer droplets may, if appropriate,contain an initiator or mixtures of initiators to trigger thepolymerization. To prepare the chelating exchanger used according to theinvention, preference is given to using initiators preferred in thepreparation of bead polymers, for example peroxy compounds such asdibenzoyl peroxide, dilauryl peroxide, bis(p-chlorobenzoyl) peroxide,dicyclohexyl peroxydicarbonate, tert-butyl peroctoate, tert-butylperoxy-2-ethylhexanoate,2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane ortert-amyl-peroxy-2-ethylhexane, and also azo compounds such as2,2′-azobis(isobutyronitrile) or 2,2′-azobis(2-methylisobutyronitrile).

The initiators are generally employed in amounts of from 0.05 to 2.5% byweight, preferably from 0.1 to 1.5% by weight, based on the monomermixture.

As further additives in the optionally microencapsulated monomerdroplets, it is possible to use porogens in order to produce sphericalbead polymers (starting material for the preparation of the monodispersechelating exchanger) having a macroporous structure. Examples ofsuitable porogens are organic solvents which do not readily dissolve orswell the bead polymer formed. Examples which may be mentioned arehexane, octane, isooctane, isododecane, methyl ethyl ketone, butanol oroctanol and their isomers.

The terms microporous or gel-like or macroporous are described in detailin the specialist literature.

The optionally microencapsulated monomer droplet can, if desired, alsocontain up to 30% by weight (based on the monomer) of crosslinked oruncrosslinked polymer. Preferred polymers are derived from theabovementioned monomers, particularly preferably from styrene.

The mean particle size of the optionally encapsulated monomer dropletsnecessary for preparing the bead polymer (starting material for thepreparation of the monodisperse chelating exchangers) is 10-1000 μm,preferably 100-1000 μm.

The functionalization of the bead polymers to produce the desiredmonodisperse chelating exchanger used according to the invention can becarried out via haloalkylation of the crosslinked polymer and subsequentconversion into the desired functional group. Methods of haloalkylatingpolymers are known from U.S. Pat. No. 4,444,961. A preferredhaloalkylating agent is chloromethyl methyl ether.

The chloromethyl methyl ether can be used in unpurified form, in whichcase it can contain, for example, methylal or methanol as secondarycomponents. The chloromethylation reaction is catalysed by addition ofLewis acids. Suitable catalysts are, for example, iron(III) chloride,zinc chloride, tin(IV) chloride and aluminium chloride.

The general preparation of heterodisperse ion-exchange resins containingchelating groups is described, for example, in U.S. Pat. No. 2,888,441,but can be applied to monodisperse ion exchangers. In this method, thehaloalkylated bead polymer is aminated and the aminated bead polymer isreacted with a suitable carboxyl-containing compound, e.g. chloroaceticacid. However, it is also possible to react the haloalkylated beadpolymer directly with suitable amino acids such as aminodiacetic acid,glycine, 2-picolylamine or N-methyl-2-picolylamine.

In a preferred form, the functionalization of the bead polymer to thedesired monodisperse chelating exchanger is carried out by directamination. For this purpose, the amidomethylation reagent is preparedfirst. To achieve this, phthalimide or a phthalimide derivative, forexample, is dissolved in a solvent and admixed with formaldehyde orparaformaldehyde. A bis(phthalimido) ether is subsequently formed fromthis by elimination of water. The bead polymer is subsequently condensedwith phthalimide derivatives. As catalyst, use is made here of oleum,sulphuric acid or sulphur trioxide.

The phthalic ester is split off to set the aminomethyl group free bytreatment of the phthalimidomethylated crosslinked bead polymer withaqueous or alcoholic solutions of an alkali metal hydroxide such assodium hydroxide or potassium hydroxide at temperatures of from 100 to250° C., preferably 120-190° C. The concentration of the sodiumhydroxide solution is in the range from 10 to 50% by weight, preferablyfrom 20 to 40% by weight. This process makes it possible to produceaminoalkyl-containing crosslinked bead polymers having a degree ofsubstitution of the aromatic rings of more than 1.

The ion exchangers to be used according to the invention aresubsequently prepared by reacting the aminated monodisperse,crosslinked, vinylaromatic base polymer in suspension with compoundswhich finally develop, as functional amine, chelating properties.

Preferred reagents are chloroacetic acid and its derivatives,formaldehyde in combination with P—H-acidic (after modified Mannichreaction) compounds such as phosphorous acid, monoalkylphosphorousesters or dialkylphosphorous esters.

Particular preference is given to using chloroacetic acid orformaldehyde in combination with P—H-acidic compounds such asphosphorous acid.

The monodisperse chelating exchangers to be used according to theinvention preferably have a macroporous structure.

EXAMPLES Example 1 1a) Preparation of the Monodisperse, Macroporous BeadPolymer Based on Styrene, Divinylbenzene and Ethylstyrene

3000 g of deionized water are placed in a 10 l glass reactor and asolution of 10 g of gelatin, 16 g of disodium hydrogenphosphatedodecahydrate and 0.73 g of resorcinol in 320 g of deionized water isintroduced and the mixture is mixed. The mixture is brought to 25° C.While stirring, a mixture of 3200 g of microencapsulated monomerdroplets having a narrow particle size distribution and comprising 3.6%by weight of divinylbenzene and 0.9% by weight of ethylstyrene (used ascommercial isomer mixture of divinylbenzene and ethylstyrene containing80% of divinylbenzene), 0.5% by weight of dibenzoyl peroxide, 56.2% byweight of styrene and 38.8% by weight of isododecane (industrial isomermixture having a high proportion of penta-methylheptane), with themicrocapsule comprising a formaldehyde-cured complex coacervate ofgelatin and a copolymer of acrylamide and acrylic acid, is subsequentlyintroduced and 3200 g of aqueous phase having a pH of 12 are added. Themean particle size of the monomer droplets is 460 μm.

The mixture is polymerized while stirring by increasing the temperatureaccording to a temperature programme commencing at 25° C. and ending at95° C. The mixture is cooled, washed on a 32 μm sieve and subsequentlydried at 80° C. under reduced pressure. This gives 1893 g of a sphericalpolymer having a mean particle size of 440 μm, a narrow particle sizedistribution and a smooth surface.

The polymer is chalky white in appearance and has a bulk density ofabout 370 g/l.

1b) Preparation of the Amidomethylated Bead Polymer

1149 g of dichloroethane, 341 g of phthalimide and 238 g of a 29.8%strength by weight formaldehyde solution are placed in a reaction vesselat room temperature. The pH of the suspension is adjusted to 5.5 to 6 bymeans of sodium hydroxide solution. The water is subsequently removed bydistillation. 24.8 g of sulphuric acid are then added. The water formedis removed by distillation. The mixture is cooled. At 30° C., 91 g of65% strength by weight oleum and subsequently 424.8 g of monodispersebead polymer prepared as described in process step 1a) are metered in.The suspension is heated to 70° C. and stirred at this temperature for afurther 6 hours. The liquid phase is taken off, deionized water is addedand residual amounts of dichloroethane are removed by distillation.

Yield of amidomethylated bead polymer: 1480 ml

Elemental analysis:

carbon: 80.7% by weight; hydrogen:  5.6% by weight; nitrogen:  3.9% byweight; balance: oxygen.

1c) Preparation of the Aminomethylated Bead Polymer

492 g of 50% strength by weight sodium hydroxide solution and 1006 ml ofdeionized water are added to 1460 ml of amidomethylated bead polymer atroom temperature. The suspension is heated to 180° C. and stirred atthis temperature for 8 hours.

The bead polymer obtained is washed with deionized water.

The total yield is 1399 ml.

Elemental analysis: nitrogen 5.8% by weight

1d) Preparation of the ion Exchanger Containing AminomethylphosphonicAcid Groups

540 ml of the moist aminomethylated bead polymer from 1c) are placed ina round-bottom flask and admixed with 281 ml of deionized water. Whilestirring, 209 g of dimethyl phosphite having a purity of 99% by weightare added dropwise over a period of 15 minutes and the mixture issubsequently stirred for another 30 minutes. 648 g of 98% strengthsulphuric acid are then metered in uniformly over a period of fourhours. After this time, the mixture is heated to 100° C., 291 g of a29.8% strength by weight formaldehyde solution is metered in at thistemperature over a period of one hour and the mixture is stirred for afurther six hours at reflux temperature.

The reaction mixture is cooled, poured onto a sieve and washed withdeionized water until the washings remain neutral. The resin issubsequently transferred to a glass column having a glass frit bottomand is converted into the sodium form by means of 3 bed volumes of 4%strength by weight sodium hydroxide solution which is introduced intothe ion exchanger bed from the top. The ion exchanger is then washedwith 5 bed volumes of deionized water. This gives 1060 ml of a moist ionexchanger.

Elemental analysis:

nitrogen:  3.2% by weight phosphorus: 10.0% by weight

Before use for the intended purpose, the ion exchanger is againtransferred to the glass column and converted into the hydrogen form bymeans of 2 bed volumes of 10% strength by weight sulphuric acid which isintroduced into the ion exchanger bed from the top. The ion exchanger isthen washed with 5 bed volumes of deionized water and removed from theglass column again.

1e) Preparation of a Sulphuric Acid Composition to be Purified by Way ofExample

3 l of deionized water are placed in a 5 l glass beaker, 1000 g of 98%strength sulphuric acid are added and, while stirring, 3.28 g ofantimony(III) chloride and 517.5 g of copper(II) sulphate pentahydrateare dissolved in the mixture. The mixture is subsequently made up to5000 g with deionized water and cooled to room temperature.

This gives a sulphuric acid containing, as intended, 30 g/l of copperand 0.4 g/l of antimony.

1f) Purification of the Sulphuric Acid Composition from 1e) According tothe Invention

100 ml of the monodisperse ion exchanger from 1d) are transferred to aglass column having a glass frit bottom (internal diameter=22 mm). Thesulphuric acid from 1e) is passed through this glass column at a volumeflow of 500 ml/h in such a way that a constant small volume of sulphuricacid is always present over the ion exchanger bed.

The sulphuric acid exiting the glass column is analysed and comparedwith the inflowing sulphuric acid from 1e).

Inflowing sulphuric acid

Concentration of antimony: 0.4 g/l

Outflowing sulphuric acid after 10 BV

Concentration of antimony: 0.02 g/l

Surprisingly, the reduction in the antimony content of the sulphuricacid to be purified by means of a monodisperse chelating exchanger issignificantly better than when using the abovementioned heterodisperseion exchangers known from the prior art.

1. A process for removing metal from a metal-containing sulfuric acidsolution, comprising: contacting the sulfuric acid solution with amonodisperse chelating exchanger.
 2. (canceled)
 3. The process accordingto claim 1, wherein the metal-containing sulfuric acid solutioncomprises a copper electrolyte.
 4. The process according to claim 1,wherein the metal is antimony, bismuth, arsenic, cobalt, nickel,molybdenum, or iron, or a combination thereof.
 5. The process accordingto claim 1, wherein the monodisperse chelating exchanger comprises atleast one functional groups of the type —(CH₂)_(n)—NR₁R₂, where R₁ ishydrogen or a CH₂COOH or CH₂P(O)(OH)₂ radical, R₂ is a CH₂COOH orCH₂P(O)(OH)₂ radical, and n is an integer from 1 to
 4. 6. The processaccording to claim 1, wherein the monodisperse chelating exchangercomprises a macroporous structure.
 7. A process for removing metal froma metal-containing copper electrolyte containing sulfuric acid,comprising: contacting the metal-containing copper electrolyte with amonodisperse chelating exchanger.
 8. A process for winning elementalcopper, comprising: providing a copper electrolyte containing sulfuricacid treated according to the process of claim 7; contacting said copperelectrolyte containing sulfuric acid with a cathode; and obtaining theelemental copper formed at the cathode by electrolytic reduction.
 9. Theprocess according to claim 7, wherein the metal is antimony, bismuth,arsenic, cobalt, nickel, molybdenum, or iron, or a combination thereof.10. A process for winning elemental copper, comprising: providing asulfuric acid solution treated according to the process of claim 3;obtaining the elemental copper formed at the cathode by electrolyticreduction.